The Modular Multi-channel Constant-current LED Driver Based On High Frequency AC Bus

With the rapid development of light-emitting diodes(Light Emitting Diode,LED)in general lighting,road lighting,landscape lighting and other lighting applications.LED driver is a core part of lighting products,and it plays an very important role in extending the lifespan of lighting products and reducing maintenance costs,also in energy saving and other aspects.In the above applications,LED driver needs to achieve three major functions:power factor correction,input and output electrical isolation,and multi-channel constant-current output.In order to improve the performance of the lighting system,in addition to meeting the above three basic functions,the LED driver should also have the advantages of low cost,high efficiency,and high reliability.Therefore,it is necessary to further explore and study high-efficiency,high-power density,low-cost solutions.Then get a simpler and more reliable LED driver.In this way,costs can be reduced,and the reliability of LED lighting drivers can be improved.And it can also extend the lifespan of semiconductor lighting systems.To this end,this paper does the following work:Firstly,the research status is summarized from the two dimensions of single-phase power factor correction and isolated multi-channel constant-current DC/DC conversion.Due to the advantages of simple topology and high device utilization,the push-pull bridgeless Boost converter is adopted to realize the power factor correction.Based on the constant current characteristics of the passive resonant network,a passive resonant rectifier is constructed.In order to simplify the circuit structure,it is needed to make the output common to as many parts as possible based on the traditional two-stage LED driver.Thus,a novel two-stage multi-channel constant current output LED driver structure and a switch multiplexing single-stage multi-channel constant current output LED driver structure are proposed.Based on the above structure,the working principle and performance of the series passive resonant constant current network are analyzed and compared.And then a passive resonant rectifier is built combined with the resonant constant current network with better performance.The LCL-T passive resonant rectifier is mainly researched,the higher harmonics is quantitatively analyzed,and an accurate solution of the output current is given by the frequency domain analysis method,which is helpful to study the accuracy of the higher harmonics on the output current.The influence of higher harmonics gives a theoretical basis for the follow-up research of LED drivers.Secondly,based on the above analysis of the higher harmonics on the average output current of the passive resonant network,a DC/DC multi-channel constant current LED driver is constructed.Considering the change of input voltage in some practical applications,a closed-loop control strategy is put forward.A parameter design method is put forward to guarantee the accuracy of the output current and the soft switching of each switch.In addition,the sensitivity of the parameters of the resonant network to the output current is analyzed,and the selection of the resonant element is guided according to the results of the sensitivity analysis.Finally,a 200 W experimental prototype was built to test and verify the correctness of the theoretical analysis,and the parameter design method.Then,a bridgeless single-stage high-frequency AC/AC resonant converter is proposed for the switch-multiplexed single-stage multi-channel constant current output LED driver structure,and the modal and performance analysis is carried out.A parameter design method is proposed in the case of output changes,which can meet the performance requirements in the full input and output range.Finally,an experimental prototype with a power of 200 W and five outputs is also built to test and verify the performance analysis results,and parameter design methods.Finally,based on the above research on single-stage LED driver,in order to further simplify the circuit structure and reduce costs,a single-stage LED drive power architecture based on variable inductance control method is proposed,which can fix the duty cycle and frequency,simplify the drive and control,effectively reduce the resonance filter network.In addition,according to the performance indicators,quantitative analysis and design of the parameters of the converter,as well as the design and elaboration of its control circuit.In the case of a fixed duty cycle of 0.5,taking into account Boost PFC unit storage capacitor voltage limit,the input voltage should not be too high,so this structure is suitable for small power applications.Finally,a relatively complete experimental scheme was determined,and a three-output experimental prototype with a power of 75 W was built for relevant experimental verification.In general,the LED driver power supply structure proposed in this paper is small in size,simple in control and high in reliability,and each additional output only needs to add a passive resonant rectifier unit,which can flexibly realize multiple constant current outputs as needed.It provide a high-efficiency,high-power density,low-cost modular solution,and it is also expected to promote the modularization and standardization of LED driver.